Abstract

A study involving laboratory experiments and reservoir simulations of gas and chemical EOR processes was performed to evaluate the EOR viability in the Mauddud reservoir of the Sabiriyah field (SAMA) in Kuwait. The subject reservoir has been under pattern waterflooding for more than 10 years. Positive response with an increase in overall oil-rate was observed during the waterflooding period until recently several wells started water production with considerable increase in overall water-cut. High degree of heterogeneity and adverse mobility ratio were the key factors contributing to the fast water-cut increase, which reduces the waterflooding recovery efficiency. Pilot simulations of EOR recovery techniques such as miscible CO2, WAG and chemical EOR processes indicated significant potential in recovery efficiency over waterflooding for the reservoir. This paper presents methodologies in designing laboratory experimental and reservoir modeling studies of EOR processes and pilot simulation design for the selected EOR process in SAMA.

One of the challenges in developing the simulation model for SAMA was to capture heterogeneity of the reservoir which impacts the fluid flow. In this paper, we show the importance of generating fine-grid model and calibrating the model with the historical production, pressure data, production logging tool (PLT) data, repeat formation test (RFT) pressure profiles, and tracer breakthrough data, to tackle the issue of capturing those details related to fluid flow behavior in the reservoir.

Data necessary for studying the surfactant-polymer (SP) chemical EOR process were collected and the suitable surfactant(s) and polymer were identified through an extensive laboratory program, which were critical in designing a chemical formulation suitable for this high temperature and high salinity carbonate reservoir. The single well chemical tracer (SWCT) tests1  performed at SAMA indicated substantial reduction in the residual oil saturation by the chosen chemical formulation. The results of the SAMA SWCT tests were incorporated in the pilot simulation model.

A field pilot program was recommended through pilot-scale simulations. A regular 5-spot pattern on approximately 5 acres is recommended in waterflooded area. The objectives of the field pilot are to 1) Identify the EOR process efficiency in terms of residual oil saturation reduction and sweep, 2) test injectivity and handling of injection and produced fluids, and 3) collect data for analyzing EOR process efficiency and for model calibration.

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